From: Jan Kara <jack@suse.cz>
To: Matthew Bobrowski <mbobrowski@mbobrowski.org>
Cc: tytso@mit.edu, jack@suse.cz, adilger.kernel@dilger.ca,
linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org,
hch@infradead.org, david@fromorbit.com, darrick.wong@oracle.com
Subject: Re: [PATCH v4 4/8] ext4: introduce direct I/O read path using iomap infrastructure
Date: Tue, 8 Oct 2019 12:52:07 +0200 [thread overview]
Message-ID: <20191008105207.GG5078@quack2.suse.cz> (raw)
In-Reply-To: <df2b8a10641ec8a0509f137dcc2db1d3cc6087f1.1570100361.git.mbobrowski@mbobrowski.org>
On Thu 03-10-19 21:34:00, Matthew Bobrowski wrote:
> This patch introduces a new direct I/O read path that makes use of the
> iomap infrastructure.
>
> The new function ext4_dio_read_iter() is responsible for calling into
> the iomap infrastructure via iomap_dio_rw(). If the read operation
> being performed on the inode does not pass the preliminary checks
> performed within ext4_dio_supported(), then we simply fallback to
> buffered I/O in order to fulfil the request.
>
> Existing direct I/O read buffer_head code has been removed as it's now
> redundant.
>
> Signed-off-by: Matthew Bobrowski <mbobrowski@mbobrowski.org>
The patch looks good to me. Just one small nit below. With that fixed, you
can add:
Reviewed-by: Jan Kara <jack@suse.cz>
> + /*
> + * Get exclusion from truncate and other inode operations.
> + */
> + if (!inode_trylock_shared(inode)) {
> + if (iocb->ki_flags & IOCB_NOWAIT)
> + return -EAGAIN;
> + inode_lock_shared(inode);
> + }
I've noticed here you actually introduce new trylock pattern - previously
we had unconditional inode_lock_shared() in ext4_direct_IO_read(). So the
cleanest would be to just use unconditional inode_lock_shared() here and
then fixup IOCB_NOWAIT handling (I agree that was missing in the original
code) in a separate patch. And the pattern should rather look like:
if (iocb->ki_flags & IOCB_NOWAIT) {
if (!inode_trylock_shared(inode))
return -EAGAIN;
} else {
inode_lock_shared(inode);
}
to avoid two atomical operations instead of one in the fast path. No need
to repeat old mistakes when we know better :).
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2019-10-08 10:52 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-03 11:32 [PATCH v4 0/8] ext4: port direct I/O to iomap infrastructure Matthew Bobrowski
2019-10-03 11:33 ` [PATCH v4 1/8] ext4: move out iomap field population into separate helper Matthew Bobrowski
2019-10-08 10:27 ` Jan Kara
2019-10-09 8:57 ` Matthew Bobrowski
2019-10-09 13:06 ` Jan Kara
2019-10-10 5:39 ` Matthew Bobrowski
2019-10-09 6:02 ` Ritesh Harjani
2019-10-09 7:07 ` Christoph Hellwig
2019-10-09 7:50 ` Ritesh Harjani
2019-10-09 9:09 ` Matthew Bobrowski
2019-10-03 11:33 ` [PATCH v4 2/8] ext4: move out IOMAP_WRITE path " Matthew Bobrowski
2019-10-08 10:31 ` Jan Kara
2019-10-09 9:18 ` Matthew Bobrowski
2019-10-09 6:22 ` Ritesh Harjani
2019-10-09 9:31 ` Matthew Bobrowski
2019-10-03 11:33 ` [PATCH v4 3/8] ext4: introduce new callback for IOMAP_REPORT operations Matthew Bobrowski
2019-10-08 10:42 ` Jan Kara
2019-10-09 9:41 ` Matthew Bobrowski
2019-10-09 6:00 ` Ritesh Harjani
2019-10-09 12:08 ` Matthew Bobrowski
2019-10-09 13:14 ` Ritesh Harjani
2019-10-03 11:34 ` [PATCH v4 4/8] ext4: introduce direct I/O read path using iomap infrastructure Matthew Bobrowski
2019-10-08 10:52 ` Jan Kara [this message]
2019-10-09 10:55 ` Matthew Bobrowski
2019-10-09 6:39 ` Ritesh Harjani
2019-10-03 11:34 ` [PATCH v4 5/8] ext4: move inode extension/truncate code out from ->iomap_end() callback Matthew Bobrowski
2019-10-08 11:25 ` Jan Kara
2019-10-09 10:18 ` Matthew Bobrowski
2019-10-09 12:51 ` Jan Kara
2019-10-10 5:44 ` Matthew Bobrowski
2019-10-09 6:27 ` Ritesh Harjani
2019-10-09 10:20 ` Matthew Bobrowski
2019-10-03 11:34 ` [PATCH v4 6/8] ext4: move inode extension checks out from ext4_iomap_alloc() Matthew Bobrowski
2019-10-08 11:27 ` Jan Kara
2019-10-09 10:21 ` Matthew Bobrowski
2019-10-09 6:30 ` Ritesh Harjani
2019-10-09 10:39 ` Matthew Bobrowski
2019-10-03 11:34 ` [PATCH v4 7/8] ext4: reorder map.m_flags checks in ext4_set_iomap() Matthew Bobrowski
2019-10-08 11:30 ` Jan Kara
2019-10-09 10:42 ` Matthew Bobrowski
2019-10-09 6:35 ` Ritesh Harjani
2019-10-09 10:43 ` Matthew Bobrowski
2019-10-03 11:35 ` [PATCH v4 8/8] ext4: introduce direct I/O write path using iomap infrastructure Matthew Bobrowski
2019-10-08 15:12 ` Jan Kara
2019-10-09 7:11 ` Christoph Hellwig
2019-10-09 13:41 ` Jan Kara
2019-10-09 11:53 ` Matthew Bobrowski
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